1, Damon: The product is dull and white. Because there is no polishing or polishing is not shaped.

2. Bubbles and impurities: There are inclusions such as bubbles and impurities in gems, which are formed in the process of making stones.

3. Cracking: Generally, it is caused by improper operation of grinding stone or cutting stone blank, and it is rare for internal stress to cause cracking.

4. Inappropriate size: It is required that the granularity, length and width error of the gem should not exceed 0.05MM. If it exceeds 0.05 mm, it is improper size, which is also called inaccurate size. Except for special requirements, the required error of some common commodities shall not exceed 0.1mm.